A two-step bonding process for preparing 6061/AZ31 bimetal assisted with liquid molten zinc interlayer: the process and microstructure

Abstract

In this study, 6061/AZ31 bimetal is manufactured utilizing the two-step bonding progress assisted with liquid molten zinc interlayer. The interfacial microstructure, phase compositions and bonding properties of 6061/AZ31 bimetal are studied. The results show that 6061/AZ31 bimetal is successfully prepared by this process. Different reaction zones are detected on the AZ31 substrate side and 6061 substrate side, which are named as aluminum-zinc reaction zone (Al-Zn RZ) and magnesium-zinc reaction zone (Mg-Zn RZ), respectively. α-Al and β-Zn are detected in the Al-Zn RZ. Mg-Zn RZ contains α-Mg, β-Zn, Al₅Mg₁₁Zn₄, Al₆Mg₁₁Zn₁₁ and MgZn₂, indicating particularly hard and brittle aluminum-magnesium intermetallic compounds (Al-Mg IMCs) are not produced. The whole process of preparing 6061/AZ31 bimetal can be divided into three stages. 6061 aluminum alloy and AZ31 magnesium alloy successively form metallurgical bonds with molten zinc. 6061/AZ31 bimetal is obtained when the liquid molten zinc solidifies again. The formation of 6061/AZ31 bimetal depends on the atomic diffusion and metallurgical reaction. Higher microhardness values are obtained in Al-Zn RZ and Mg-Zn RZ compared with 6061 substrate and AZ31 substrate. The maximum interface microhardness (333 HV) of 6061/AZ31 bimetal is obtained in the MgZn₂ layer of Mg-Zn RZ. The maximum shear strength of 6061/AZ31 bimetal is 38.7 MPa, and fracture occurs in the MgZn₂ layer. The fracture morphology exhibits the characteristics of brittle fracture.

Keywords:

• 6061/AZ31 bimetal
• bonding progress
• molten zinc
• microstructure
• formation mechanism

Acknowledgments

The authors gratefully acknowledge the Advanced Materials Testing and Analysis Center of Hebei University of Technology.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is financially supported by the Natural Science Foundation of Hebei Province, PR China under Grant No. E2020202011.